#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>

int Dan(int arr[], int sz)
{
	int i = 0;
	int ret = 0;
	for (i = 0; i < sz; i++)
	{
		ret ^= arr[i];
	}
	return ret;
}
int main()
{
	int arr[9] = { 1,2,3,4,5,1,2,3,4 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	int ret = Dan(arr, sz);
	printf("%d", ret);
	return 0;
}